The present invention generally relates to electronic throttle security, and more particularly relates to such security for internal combustion engines having electronic throttle control systems for enabling cylinder activation and deactivation.
Those skilled in the art of internal combustion engine design understand that control of internal combustion engines preferably includes engine cylinder activation and deactivation or displacement on demand to improve fuel economy. This engine control strategy generally involves reducing the number of active engine cylinders as a reduced amount of power is requested from the engine, and the valves of deactivated cylinders are generally configured to improve fuel efficiency. For example, the valves of the deactivated cylinders are at least substantially closed to reduce pumping losses. However, in this example, after some of the cylinders are at least substantially closed to reduce pumping losses, the remaining active cylinders are generally configured to receive a throttle increase to maintain the same level of output torque from the engine. Furthermore, when the power requirements increase a sufficient amount, the deactivated cylinders are reactivated and the throttle level is altered so that the engine continues to deliver the desired amount of power.
It is desirable for the adjustments of the control strategy to occur with minimal, and preferably no awareness of the engine operator. This statement is particularly true in the case of an automobile engine operating under the control of an operator that is providing a substantially constant accelerator pedal position. In this situation, the engine throttle is preferably adjusted a predetermined amount in response to cylinder deactivation and preferably adjusted a predetermined amount in response to cylinder reactivation. While these control strategies for internal combustion engines provide the proper engine power and improve fuel efficiency, other improvements are continually sought.
In view of the foregoing, it should be appreciated that there is a need to provide methods and apparatus for providing security for electronically controlled cylinder activation and deactivation. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention, brief summary of the invention, abstract, and appended claims, taken in conjunction with the accompanying drawings and this background of the invention of the invention.
In accordance with the teachings of the present invention security methods and apparatus are provided for ensuring that a throttle increase accompanying a decrease in the number of active cylinders of an internal combustion engine will be limited to a predetermined threshold period with more than a selected fraction of all the cylinders of the engine being activated. The apparatus comprises an electronic controller that generates the throttle increase if less than all the cylinders are requested to be activated. A query is made to determine if the number of cylinders being fueled is equal to or less than the selected fraction. A timer is started if the number of cylinders being fueled is greater than the selected fraction of all the cylinders. The throttle increase is turned off if the amount of time measured by the timer exceeds the predetermined threshold before the number of cylinders being fueled becomes either less than or equal to the selected fraction.